In a process of forming a wire structure, there is a case of performing plasma etching to form a damascene-structure concave portion constituted by a groove or a via hole on various layers formed on, for example, a semiconductor wafer (“wafer”).
A plasma etching apparatus that performs the plasma etching process is configured, for example, by placing an upper electrode and a placing table serving as a lower electrode in a processing chamber under a vacuum state. While the wafer is placed in the placing table, plasma is generated and ions are injected into the placing table by applying a high-frequency power at a predetermined frequency to the upper electrode and the placing table through a matching unit to thereby perform an etching process. An electrostatic chuck in which the wafer is placed on the surface thereof and a focus ring surrounding an outer periphery of the wafer placed in the electrostatic chuck are installed in the placing table. The electrostatic chuck serves to control the temperature of the wafer by adsorbing the wafer and transferring heat to the wafer. The focus ring is installed to distribute plasma on the surface of the wafer with high uniformity and etched together with the wafer by the ions.
However, the electrostatic chuck and the wafer have different thermal expansion coefficients, such that when the wafer is placed on the electrostatic chuck, the electrostatic chuck and the wafer rub against each other due to the difference between the thermal expansion coefficients. As a result, when the processing of the wafer is repeatedly continued, the surface of the electrostatic chuck is gradually planarized to increase a contact area between the placing table and the wafer, such that a transfer rate of heat to the wafer is changed, and as a result, an etching characteristic of the wafer is changed. Further, when the etching process of the wafer is repeatedly performed, the focus ring is also etched, and as a result, the shape of the corresponding focus ring is gradually changed. The change in the shape results in changing an injection direction of the ions or a formation state of an electric field, thereby changing the etching characteristic of the wafer.
In order to remove an adherend attached to a wall surface or the placing table within the processing chamber after etching, cleaning may be performed, in which a gas supplied into the processing chamber turned into plasma to remove the adherend. Protecting the electrostatic chuck by placing a dummy wafer on the electrostatic chuck has been considered in the cleaning. However, it has been considered that the cleaning is performed without using the dummy wafer in order to save time or reduce the cost required to transport the dummy wafer into the processing chamber. However, when the dummy wafer is not placed as such, the surface of the electrostatic chuck may be chamfered by the cleaning, such that the transfer rate of the heat to the wafer is changed, thus, the etching characteristic of the wafer is changed.
As such, the state of the surface of the electrostatic chuck and the shape of the focus ring are changed due to the consumption resulting from the etching process, and as a result, the etching characteristic is changed. Therefore, a precise state management is required. When the shape is out of an allowable range, an action such as an immediate replacement is needed.
However, since the electrostatic chuck and the focus ring are installed in the vacuum state as described above, installing a sensor in the processing chamber is considered in order to check the states of the electrostatic chuck and the focus ring in the vacuum state. However, plasma may be misaligned due to the installation of the sensor. Therefore, based on a tendency of the change in the state of the surface of the electrostatic chuck and the shape of the focus ring in the related art, usable durations (life-spans) of the electrostatic chuck and the focus ring are set, and when a plasma etching duration exceeds the set durations, the processing chamber is opened to the atmosphere to replace the electrostatic chuck and the focus ring. Further, when the change in etching characteristic in the wafer is verified, the processing chamber is opened and the states of the electrostatic chuck and the focus ring are checked. When the shape is out of the allowable range, the electrostatic chuck and the focus ring may be replaced.
However, since the change degrees in the shapes of the electrostatic chuck and the focus ring are different according to the difference in etching conditions, it is difficult to manage the states of the electrostatic chuck and the focus ring precisely by using a technique of setting the usable durations as described above. In the technique of verifying the change in etching characteristic of the wafer, and thereafter, replacing the electrostatic chuck and the focus ring, the wafer is wasted. As a result, it is difficult to acquire the stable etching characteristic over a long period. In the technique, since the processing chamber is opened to the atmosphere when replacing the electrostatic chuck and the focus ring, an etching process cannot be accomplished until a desired vacuum degree is acquired by vacuum-exhausting the processing chamber after the processing chamber is opened to the atmosphere. Therefore, productivity of the plasma etching apparatus may deteriorate. Japanese Patent Application Laid-Open No. 2009-16447 discloses a substrate processing apparatus having the plasma etching apparatus, but a technique of solving the problem is not disclosed.